MODEL RELEASED. Heart surgery. Surgeon making a chest incision by diathermy during coronary artery bypass surgery. Diathermy is the production of heat from a high-frequency electric current. There is little blood loss from incisions made in this way. In coronary artery bypass surgery, lengths of vein are taken from the legs and attached to the heart to bypass narrowed or blocked coronary arteries. The coronary arteries supply the heart muscle with oxygen and nutrients. Photographed at The Royal Infirmary, Edinburgh, Scotland.